JPH0228529Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic copying machine equipped with a document detection device that detects the density and size of a document to be copied.

In an electrophotographic copying machine, copies are made from originals of various densities and sizes. Therefore, conventional electrophotographic copying machines are equipped with a density adjustment device so that the optimal copy image can be obtained for documents of any density and size. The density is adjusted manually. Regarding the size, the recording paper corresponding to the original size is selected by visually checking the size code displayed on the cassette or the like or the code displayed on the panel. However, such manual density adjustment is cumbersome, so the density and size of the original are automatically detected before copying, the image density is automatically adjusted, and the paper feed size is automatically selected. A copy machine has been proposed.

Conventionally, as a method of detecting the density of the original and automatically adjusting the image density, for example,
As proposed in Publication No. 93834, there is a known method of controlling density conditions from the maximum and minimum density values, but it is possible to For originals with dark images, there is a problem in that the density conditions are adjusted for printed ruled lines. Therefore, as in JP-A-55-120623, a histogram corresponding to the density distribution of each point on the document is created by scanning the document placed on the document table, and the pattern of this histogram is used to create a histogram. A method of adjusting the image density to a certain value has been proposed, but the circuit configuration for creating the histogram becomes complicated.

On the other hand, the conventional method for detecting document size is to place multiple sensors at predetermined positions on the document holding cover and detect the document size based on the output status of these sensors, which is completely separate from the method of detecting the density of the document. There are known ways to do this. This method has a problem in that the structure of the document holding cover becomes complicated and costs increase.

In consideration of the above points, the present invention is capable of automatically detecting the density and size of the original at the same time. A document detecting member is provided that moves along a predetermined path determined in relation to a predetermined document placement position for each document size on the placing table in conjunction with the closing operation of the document holding cover. At the same time, the document size or document density is determined based on a signal from an optical sensor provided in a part of the document.

The present invention will be explained below based on the drawings.

1 and 2 show the operating principle of the document detection device according to the present invention. In Figure 1, 1
2 is a document table usually made of a transparent glass plate or the like on which the original to be copied is placed; 2 is a sensor bar placed on the bottom of the document table 1 near the side edge of the document table 1; The lower side of the document table 1 can be rotated horizontally about the fulcrum C of the document table 1 along the plane of the document table 1 as shown by the dashed line. A sensor 21, such as a reflective optical sensor, which will be described later, is attached to the upper surface of the other end of the sensor bar 2.

Place the size B5, B4, A4,
When a document such as A3 is placed and the sensor bar 2 is rotated, the sensor bar 2 starts to detect light reflected from the document at point D for A3 and A4 size documents, and starts to detect light reflected from the document at point E (size A4 ) and point F (size
(For A3) to end the detection. Furthermore, for B-series originals B4 and B5, detection of reflected light from the originals starts at point G, and ends at point H (for size B5) and point I (for size B4). As a result, the sensor output becomes as shown in FIG. Second
The four types of manuscript sizes shown in the figure are A4, A3, B5,
Looking at the document size A4 of B4, the document (size
A4) The length of this time t is determined by the document size, so by measuring this time t, the document size can be determined. Further, the output level of the sensor changes as shown in the figure, depending on the density of the document during time t. That is, since there is little light reflected from text or graphic parts (usually black) of the document, the sensor output is small, but since there is a lot of light reflected from other parts (the normal surface of the document), the sensor output becomes large. Therefore, the original density can also be detected based on the average level of the sensor output at this time t.

FIG. 3 is a schematic diagram showing the structure of an embodiment of the document detection device according to the present invention. In FIG. 3, reference numeral 3 denotes a document holding cover that rotates around a shaft 3a on one side edge, and a lever 4 that rotates together with the shaft 3a is fixed to one end of the shaft 3a. One end of the wire 5 is tied to. 6 and 7 are pulleys that guide the wire 5. The other end of the wire 5 is wound and fixed around a pulley 9 which is biased clockwise by a return spring 8. Pulley 9
One end of the sensor bar 2 is fixed to the sensor bar 2, and the fixed end serves as a rotation fulcrum C of the sensor bar 2.

FIG. 4 is an enlarged cross-sectional view of the sensor 21 provided at the tip of the sensor bar 2 using a reflective optical sensor.
a and a light receiving element 21b, the light emitting lamp 21
The light generated from a is reflected by the document M (indicated by a two-dot chain line), is received by the light receiving element 21b, and is extracted as an electrical output.

FIG. 5 shows a detection circuit of the document detection device according to the present invention, in which numeral 21 is a sensor, and 10 is a document size determination circuit that compares the output from the sensor 21 with document size data stored in the storage circuit 11 to determine the document size. , 12 is a recording paper selection circuit that selects a recording paper based on the output of the original size discrimination circuit, and 13 is a sensor 21.
A document density determination circuit 14 determines the document density by comparing the output from the document density determination circuit 13 with document density data stored in the storage circuit 11 .

Next, the document detection operation will be explained based on FIGS. 1 and 3.

As can be seen from FIG. 3, when the document holding cover 3 is first lifted, the wire 5 is loosened and the sensor bar 2 and sensor 21 are biased by the return spring 8 and are in the position shown. Therefore, when a document (for example, size B5) is placed on a predetermined position on the document table 1 and the document holding cover 3 is started to be lowered, the wire 5 is pulled in the direction of the broken line, and the pulley 9 is pulled back by the return spring 8.
is rotated counterclockwise. In addition, lever 4
The pulley 9 is configured so that the detection operation by the sensor 21 can be completed by only slightly pushing down the document holding cover 3. As a result, the sensor bar 2 and the sensor 21 rotate as shown by the dashed line in FIG. At this time, the sensor 21 in FIG.
Only during the period t' after the start of rotation, the output level rises vertically at point G, which crosses the side edge of the document, due to the reflected light from the document, as shown in FIG. This time t' is determined by the recording circuit 1 in the document size discrimination circuit 10 shown in FIG.
It is compared with the original size data stored in No. 1, and it is determined from the time ratio that the original size is B5. The recording paper selection circuit 12 performs a recording paper selection operation based on the output from the original size determination circuit 10. There are various ways to select recording paper, but for example, a plurality of recording papers of different sizes may be loaded in a cassette into a copying machine, and the paper feeding mechanism for the cassette of the original size determined by the original size determination circuit 10 may be used. There is a way to make it work.

Meanwhile, during time t', the original density determination circuit 13 compares the level of the signal output from the sensor 21 with the original density data stored in the storage circuit 11 to determine the density of the original. The density control circuit 14 appropriately controls the density based on the output from the original density determination circuit 13. Various concentration control methods are known and are not the subject matter of the present invention, so they will not be described in further detail.

FIG. 6 shows an embodiment of a sensor bar drive mechanism using an electric circuit.

20 is a micro switch that is turned on at the same time as the document holding cover 3 is operated in the closing direction; 23 is a timer that outputs an "H" level signal for a certain period of time; 24 is a relay consisting of a coil 24a and a contact 24b; 25 is a motor; 26 is a worm gear rotated by the motor 25, 27 is a worm gear 2
6, and this gear 27 has a shaft 27a.
The sensor 21 is fixed via. Shaft 27a
is biased clockwise by the return spring 8 as in FIG.

When the original is placed at a predetermined position on the original table 1, the original holding cover 3 is placed on the original, and the original holding cover 3 is operated slightly in the closing direction, the micro switch 20 is turned on, and the timer 23 turns on the “H” for a certain period of time. ”
A level signal is output. As a result, the coil 24a of the relay 24 is energized and the contact 24b is closed, so the motor 25 is driven and the sensor bar 2 and the sensor 21 are driven.
is rotated counterclockwise through the worm gear 26 and the gear 27 against the return spring 8. The timer 23 is set to output an "H" level signal during the time required for the sensor bar 2 to scan the document table 1 and until the document holding cover 3 reaches the document table 1. When this is completed, the sensor bar 2 is returned to its normal position by the return spring 8. While the sensor 21 scans, the size and density of the document are detected, and the method for this detection is as already explained with reference to FIGS. 1, 2, and 5.

The above embodiment is an example in which a document placed on a document table is scanned along the surface of the document table to simultaneously detect the size and density of the document.
The two embodiments shown in the figures are examples in which only the size of the document is detected without detecting the density of the document.

First, the embodiment shown in FIGS. 7 and 8 shows the main part of a document size detection device for an electrophotographic copying machine with a fixed document table. A lever 3 extends rearward approximately at the center of one end of the document holding cover 3 that rotates around a fulcrum D.
0 is provided, and the micro switch 31 is turned on by the lever 30 at the same time as the document holding cover 3 is operated in the closing direction. On the other hand, a pair of movable plates 32 are provided below the rear of the document table 1, and a light emitting element 33, for example, is provided on the front upper surface of the movable plate 32.
A size detection element group 33, 34, 35 consisting of a light receiving element 33b and a light receiving element 33b is provided, and a rack 32a is provided on the lower surface in the longitudinal direction. The number and position of the size detection elements are determined in consideration of the type of document size, and in the illustrated example, there are three size detection elements 33, 3 that cover A series sizes.
4 and 35 are arranged at equal intervals, and two of these three size detection elements cover the B series size. Further, the movable plate 32 is provided with a return spring 38 that always urges it backward. A pinion 36 is located below the moving plate 32.
is disposed and engages with the rack 32a of the movable plate 32, and the pinion 36 is rotationally driven by a motor 37. A timer 39 outputs an "H" level signal for a certain period of time after the microswitch 31 is turned on.

Now, a document M of an arbitrary size (for example, B5 size) is placed on the document table 1, and the document M is held down by the document holding cover 3. When the document holding cover 3 is operated in the closing direction, the micro switch 31 is turned on and the motor 37 is driven to rotate. As a result, the pinion 36 rotates in the direction of the arrow, and the moving plate 32 moves forward in the direction of the arrow against the return spring 38. For B5 size originals, size detection elements 34 and 3
The light receiving element 5 detects and outputs the reflected light from the document, but the light receiving element 33 among the size detecting elements does not detect the document M and has a different output level. This output state continues while the moving plate 32 moves forward, and the moving plate 32
When the size detection elements 33, 34, and 35 pass the front edge of the document M at the position indicated by the dashed line in FIG. 7, the output levels of the size detection elements 33, 34, and 35 all become zero. Therefore, the document size can be detected from changes in the output levels of these three size detection elements 33, 34, and 35 and the time taken until the total output level becomes zero. The movable plate 32 moves forward for the time set by the timer 39, and when the set time elapses, the rotation of the motor 37 is stopped and the moving plate 32 is returned to the initial position backward by the return spring 38.
That is, it is evacuated from below the document table 1 so as not to interfere with the subsequent exposure process. The method for determining the document size based on the outputs from the size detecting elements 33, 34, and 35 is almost the same as in the other embodiment shown in FIG. 5, so a description thereof will be omitted.

The embodiment shown in FIGS. 9 and 10 shows the main part of a document size detection device for an electrophotographic copying machine with a movable document table. Reference numeral 1 denotes a movable document table, on which a document M is placed at a predetermined position. A plurality of size detection element groups (nine in this embodiment) are arranged below the document table 1 so as to cover the entire surface of the document table 1. Each size detection element is composed of a light emitting element and a light receiving element, and the light emitted from the light emitting element is reflected from the back surface of the document and received by the light receiving element, which is the same as in the embodiment described above. In addition,
40 is an original exposure lamp. Now, assuming that the nine size detection elements are 41 to 49, as shown in FIG. 10, when an original M is placed, the reflected light from the original is detected by the size detection elements 48 and 49, and Since the size detection elements do not receive reflected light, the document size can be determined from the output state of the nine size detection element groups, which is the same as in the embodiment described above.

After the document size is detected, the document table 1 moves in the direction of the arrow, and exposure scanning of the document starts.

Several embodiments of the document detection device of the present invention have been described above, but the document table surface scanning method is not limited to the one in which one sensor scans from one edge of the document table to the other edge as illustrated. Of course, it is also possible to use a system in which the document table is scanned separately in the longitudinal direction and the width direction.

As explained above, in the present invention, a device is installed at the lower part of the transparent document placing table, and is moved along a predetermined path that is related to the document placing position determined for each document size on the document placing table. A document detecting member is provided, and the document detecting member is moved from outside the document placement area, through the document placement area, and back to outside the document placement area in conjunction with the closing operation of the document holding cover prior to a series of copying operations. The size and density of the original can be determined at the same time or either of these based on the signal from the optical sensor provided in a part of the original detection member, so the size and density of the original can be detected at the same time. . Further, since the document size detection means is provided at the lower part of the transparent document table, the document size can be detected prior to the copying operation. This eliminates the waste of feeding and copying recording paper of a size different from the original size, and has the effect of making the copying operation always smooth.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the operating principle of the document detection device according to the present invention, Fig. 2 is an output waveform diagram of the sensor bar for each document size, and Fig. 3 is an implementation of the detection member drive mechanism of the document detection device according to the present invention. For example, FIG. 4 is a cross-sectional view of the main part of the sensor bar which is a detection member, FIG. 5 is an electric circuit diagram of the document detection device according to the present invention, and FIG.
The figure shows another embodiment of the detection member driving mechanism, and FIGS. 7 and 8 show an embodiment of the detection device according to the present invention.
7 is a side view, FIG. 8 is a plan view, FIGS. 9 and 10 are other embodiments of the detection device according to the present invention, and FIG. 9 is a partially sectional side view of the document size detection device, FIG. 10 is a plan view thereof. DESCRIPTION OF SYMBOLS 1... Original table, 2... Sensor bar, 3... Original holding cover, 8, 38... Return spring, 10... Original size determination circuit, 11... Memory circuit, 12...
Recording paper selection circuit, 13... Original density determination circuit, 1
4... Concentration control circuit, 20, 31... Micro switch, 23, 39... Timer, 21... Sensor, 24... Relay, 32... Moving plate, 33-3
5,41-49...Size detection element, 40...Original exposure lamp.

Claims (1)

[Scope of utility model registration request] A transparent document holding table on which a document to be copied is placed; an openable/closable document holding cover that covers the document placing table; When the document presser cover closes in conjunction with the closing operation of the presser cover, it moves from outside the document placement area through the document placement area, and when the document presser cover is completely closed, it moves from the document placement area again to the outside of the document placement area. A document detecting member that moves along a predetermined path so as to exit the document, and has an optical sensor in a part thereof, and determines the document size or document density based on a signal output from the optical sensor as the document detecting member moves. An electrophotographic copying machine characterized by comprising: a determining means.